Polyamides and polyesters have been used in prior art laminates but are unsuitable in a number of applications. For example, polyamides are not weather-resistant since they age when exposed to light and absorb moisture from the atmosphere. This leads to discoloration, deterioration of the mechanical properties and warpage phenomena. Although polyamides have good mechanical properties, particularly good toughness, they have an intrinsicly poor barrier action; for example, polar substances can easily migrate through polyamides. This is a serious disadvantage in, e.g., motor fuel lines in which alcohol-containing fuel is conveyed.
Polyesters are generally highly weather-resistant and have outstanding barrier action against both polar and nonpolar media. However, they are generally impact-sensitive, and, in particular, the notched bar impact strength is unsatisfactory. Polyesters therefore cannot be used in many applications where properties such as high thermal stability and good toughness are desired.